Impact wrench



Feb. 20, 1968 ca. E. MAFFEY, JR.. ETAL 3,369,615

IMPACT WRENCH Filed May 2'7, 1966 2 Sheets-Sheet 1 INVENTORS GEORGE E. MAFFEY, JR. WILLIAM D. ABELL ATTORNEY Feb. 20, 1 968 e, E. MAFF EY, JR. ETAL 3,359,615

IMPACT WRENCH Filed May 2'7, 1966 2 Sheets-Sheet 2 f V i gASA 25A 1" m/ /r.\\ LLALJ 'fi 23 26 23A I2 INVENTORSQ GEORGE E. MAFFEY,JR.

WILLIAM D. ABELL ATTORNEY 3,3 $9,515 Patented Feb. 20, 1968 Fire 3,369,615 IMPACT WRENCH George E. Maifey, Jr., Timonium, and William I). Abel], Manchester, Md., assignors to The Black and Decker Manufacturing Company, Towson, Md, a corporation of Maryland Filed May 27, 1966, Ser. No. 553,383 8 Claims. (Cl. 17393.6)

The present invention relates to a portable power-driven tool, and more particularly, to a portable electric impact wrench having speed-reduction planetary gearing and a cooperating impact clutch mechanism both designed to achieve minimum axial length, thereby enhancing the overall compactness, convenient usage, and portability of the tool.

It is a specific object of the present invention to provide, for use in a tool of the character described, the combination of a wall serving as a partition between the motor housing and the clutch housing; a bearing means formed within the wall; a motor shaft journaled in the wall and extending into the clutch housing; a clutch spindle having an integrally-formed rearwardly-extending tubular portion supported within the bearing means in the wall, radially of the motor shaft; a pinion on the end of the motor shaft; a radially-enlarged planet gear carrier mounted on the spindle; intermediately of its length, for conjoint rotation therewith; planet gears carried by the planet gear carrier, engaging the pinion; and an internal ring gear formed integrally with the partition wall and engaging the planet gears.

It is another specific object of the present invention to provide, for use in a tool of the character described, the combination of :a spindle rotatably supported within the clutch housing; a radially-enlarged planet gear carrier mounted on the spindle for conjoint rotation therewith; a hammer mounted coaxially on the spindle forwardly of the planet gear carrier; an anvil having clutch teeth cooperating with teeth formed on the hammer; means for imparting axial and rotary movement to the hammer relative to the spindle; whereby the hammer has axially advanced and retracted positions and is adapted to deliver a series of rotary impacts to the anvil; and whereby in its retracted position, the hammer telescopes over the planet gear carrier on the spindle; a first recessed annular groove formed in the hammer, accessible rearwardly of the hammer; a second recessed annular rgoove in the planet gear carrier, accessible forwardly of the spindle; and a coil spring disposed coaxially of the spindle and nested axially between the first and second recessed annular grooves, respectively, whereby the overall mechanism has minimum :axial length for greater compactness.

In a preferred embodiment, the coil spring is seated upon an annular row of 'balls disposed within the first recessed annular groove formed in the hammer, thereby providing a convenient and economical thrust bearing means for the impact clutch mechanism; the rearwardlyextending tu bular portion of the spindle bears against a bearing retained within the partition wall, thereby taking up axial thrust loads in the rearward direction; the retaining plate, moreover, is secured to the partition wall and draws the wall up tight against a ring seated in an annular groove rearwardly adjacent to a portion of the partition wall, with the retaining plate in turn being keyed to the motor housing to prevent rotation of the plate; and the partition wall portion comprises an axially-extending annular flanged portion Within which the internal ring gear (of the speed-reduction planetary gearing) is integrally formed.

With this arrangement, the length of the coil spring (which is synonomous with the required spring force) becomes the limiting dimensions, and all of the other components are designed around the spring length so as to obtain minimum axial length, hence maximum compactness of the overall tool.

These and other objects of the present invention will become apparent from a reading of the following specification, taken in conjunction with the enclosed drawings, in which:

FIGURE 1 is a side elevation of the improved impact wrench of the present invention, with parts broken away and sectioned to illustrate the improved construction;

FIGURE 2 is a transverse section, taken along the lines 22 of FIGURE 1, and showing the retaining plate for anchoring the partition wall between the motor housing and the clutch housing;

FIGURE 3 is a transverse section, taken along the lines 33 of FIGURE 1, and showing the pinion formed on the motor shaft for engaging the planet gears, and the planet gears in turn engaging an internal ring gear formed integrally within the partition wall;

FIGURE 4 is a transverse section, taken along the lines 4-4 of FIGURE 1, and showing the spindle, the hammer mass coaxially mounted on the spindle, and the coil spring nested within a second recessed annular groove formed within the planet gear carrier, the planet gear carrier being formed integrally with the spindle for conjoint rotation;

FIGURE 5 is a transverse section, taken along the lines 55 of FIGURE 1, and showing the spindle, the hammer coaxi ally mounted on the spindle; and an annular row of balls within the first recessed annular groove in the hammer for seating one end of the coil spring;

FIGURE 6 is a transverse section, taken along the lines 6-6 of FIGURE 1, and showing the reduced forward end of the spindle being piloted within the anvil shank, and further showing the manner in which the cooperating clutch teeth on the hammer and anvil, respectively, engage each other at the moment of impact;

FIGURE 7 is an exploded view of the individual elements of the improved mechanism of the present invention; and

FIGURE 8 is a section view, taken along the lines 8-8 of FIGURE 2, and showing the manner in which the retainng plate secures the partition wall between the motor housing and the clutch housing, and further showing the manner in which the retaining plate is keyed to the motor housing.

With reference to FIGURE 1, an impact wrench 10 is illustrated for convenience, and it will be appreciated that the wrench is indicative of a class of portable poweroperated tools within which the teachings of the present invention may be incorporated. With this in mind, the impact wrench 10 has a generally-cylindrical main housing 11 comprising a motor housing 12 formed integrally with a transmission or clutch housing 13 extending forwardly therefrom. A rear end cap 14 is secured rearwardly of the motor housing, and the end cap 14 has a pair of brush holders, one of which is shown as at 15. The motor housing has a depending portion 16 which cooperates with a rear cover 17 to form a pistol-grip handle for the tool. The handle has a switch actuated by means of a trigger 18; preferably, this trigger is adapted for one hand forward or reverse operation in a manner disclosed and claimed in the copending Maffey, 11. application, Ser. No. 483,650, filed Aug. 30, 1965, entitled Pivoted Trigger Means for Reversible Pistol-Grip Tool, and assigned to the assignee of the present invention.

With reference again to FIGURE 1, and with further reference to FIGURES 2 and 8, a wall 19 serves as a partition between the motor housing 12 and the clutch housing 13. The wall 19 is provided with an axiallyextending annular flanged portion 1% seated on a first annular ledge or shoulder formed Within the clutch housing 13. A ring 21 is seated in an annular groove 22 formed in the motor housing 12, rearwardly adjacent to the flanged portion 19a of the partition wall 19. A retaining plate 23 is disposed rearwardly adjacent to the partition wall. The retaining plate 23 has integral tabs or protuberances 24 keyed within slots 25 formed Within the motor 12, thereby preventing the retaining plate 23 from rotating. The retaining plate 23 rests upon a second annular ledge or shoulder 25a formed within the motor housing 12. The retaining plate 23 has a plurality of dimpled identations 23a which are received in a corresponding plurality of pockets 19b formed in the partition wall 19, thereby keying the retaining plate 23 to the partition wall 19. The retaining plate 23 is secured to the partition wall 19 by means of a plurality of screws 26. In this manner, the partition wall 19 is drawn up tight against the ring 21, and to a certain extent, separates from the annular groove 20 in the clutch housing 13.

With reference again to FIGURE 1, and with further reference to FIGURES 3 through 7, the motor housing 12 is provided with a suitable electric motor (not shown) which has a shaft 27. The shaft 27 has a sleeve 28 pressed thereon to cover the pinion cutter runout 27a. The sleeve 28 also provides the hub portion of an integrally-molded plastic fan 29. A hollow-cylindrical bearing, preferably comprising a sleeve 30, is pressed within a bore 31 within the partition wall 19. A second hollow-cylindrical bearing, preferably comprising a sleeve 32, has a running fit over the sleeve 28 on the armature shaft 27. A spindle 33 is mounted within the clutch housing 13 in substantial coaxial alinement with the motor shaft 27. The spindle 33 has a radially-enlarged portion 34 serving as a planet gear carrier. This planet gear carrier 34 is disposed intermediately the length of the spindle and is mounted thereon for conjoint rotation. Preferably, the spindle 33 and the plant gear carrier 34 are formedas individual pieces, and then are pressed together to form a single member, as shown in FIGURE 1.

The planet gear carrier 34 has an integrally-formed rearwardly-extending tubular portion 35 which is received with a running fit between the bearing sleeves and 32. To this extent, the bearing sleeves 30 and 32 are coaxially nested and are disposed radially of one another, one between the partitionwall 19 and the rearwardly extending tubular portion of the spindle 33, and the 1 other between the tubular portion 35 and the motor shaft 27. This radial stacking of the bearing sleeves 30 and 32 distinguishes from the prior art usage of axially-spaced bearings, hence reduces the axial length of the tool and enhances its overall compactness. Moreover, the bearing sleeve 30 abuts against the retaining plate 23, so that the retaining plate 23 takes the rearward axial end thrust of the spindle 33.

Pins 36 are secured within the planet gear carrier 34, and planet gears 37 are mounted with a running fit upon the pins 36. These planet gears 37 engage, first, a pinion 38 formed on the forward end of the motor shaft 27, and secondly, an internal ring gear 39. This internal ring gear 39 is formed integrally with the axially-extending annular flanged portion 19a of the partition wall 19.

The forward end of the spindle 33 is reduced as at 40 and is piloted within a blind axial bore 41 formed in the shank portion 42 of an anvil 43. This anvil 43 is journaled Within a bearing sleeve 44 retained within the front end of the clutch housing 13, and a suitable seal 45 is provided between the bearing sleeve 44 and the anvil shank 42. The anvil shank 42 has a suitable non-circular portion, as at 46, for cooperating with a usual driving socket,

the latter being omitted. Preferably, a nose piece 47 is mounted over the end of the clutch housing 13, radially of the anvil shank 42. The bearing sleeve 44, as well as the bearing sleeves 30 and 32 in the partition wall 19,

may com-prise hollow-cylindrical roller (or needle) bearings, if desired.

With reference again to FIGURES 1 and 4 through 7, a hammer 48 is coaxially, mounted upon the spindle 33. The spindle 33 has a pair of cam grooves 49, each of which receives a steel ball 50, and the balls 50 are received within ball raceways 51 formed internally of the hammer 48. The respective combinations (of the steel ball 50 and the cam groove 49) provide a well-known cam means formed between the hammer 48 and the spindle 33 for imparting axial and rotary movement to the hammer relative to the spindle. In this manner, the hammer 43 has axially advanced and theretracted positions. The advanced position of the hammer 48 is illustrated by the full section lines in FIGURE 1, while its axially-retracted osition is illustrated by the broken lines. Accordingly, the hammer 48 is adapted to deliver a series of rotary impacts to the anvil 43 in a manner well known in the art. To this end, the hammer 48 has clutch teeth 52a cooperating with clutch teeth 52b formed on the anvil 43. The clutch teeth 52b on the anvil 43 are in the nature of radially-extending integrally-formed lugs which are supported upon an axial thrust washer 53. The hammer 48, in its rearWardly-retracted position, telescopes over the planet gear carrier 34 on the spindle 33, thereby achieving a degree of compactness heretofore not available in the art.

The hammer 48 has a first recessed annular groove 54 formed therein. This groove 54 is accessible rearwardly of the hammer. A second recessed annular groove 55 is formed within the planet gear carrier 34 of the spindle. This second groove 55 is accessible forwardly of the spindle. An annular row of balls 56 is received Within the bottom of the first recessedannular groove 54 in the hammer 48; A coil spring 57 is disposed coaxially of the spindle 33 and is nested axially between the first and.

second recessed annular grooves 54 and 55,: respectively. This coil spring 57 constantly urges the cooperating clutch teeth 52a and 52b into engagement With one another, with disengagement being provided by the cam means comprising grooves 49 and balls 50.

The following special. features of the improved construction, in combination with one another, achieve the objectives of minimum axial length: (1) The coil spring 57 is nested within the recessed annular grooves 54, 55v

formed within the hammer 48 and planet gear carrier 34, respectively; (2) the annular row of balls 56 seats one end of the spring 57 and provides a convenient thrust bearing means; (3) the hammer 48 telescopes over the planet, gear carrier 34 in the retracted position of the hammer; (4) the internal ring gear 39 is formed integrally with the partitionswall 19; and (5) the bearing sleeves 30 and 32 are stacked, radially, within the partition wall. All of these features contribute to the minimized axial length of the driving mechanism, hence achieve the desired objectives of tool compactness, handling ease, and convenience-consonant with tool performance and reliability at reduced manufacturing cost.

Obviously, many modifications may be made without departing from the basic spirit of the present invention; and accordingly, within the scope of the appended claims,

the invention may be practiced other than hasbeen spe.

cifically described herein.

We claim:

1. In an impact wrench mechanism, the combination of:

(A) a spindle having a radially-enlarged rearward portion;

(B) a hammer coaxially mounted on the spindle forwardly of its rearward portion;

(C) an anvil forwardly of the hammer;

(D) cooperating clutch teeth formed on the anvil and hammer, respectively;

(E) means for imparting axial and rotarymovement to the hammer relative to the spindle, whereby the hammer has axially advanced and retracted positions and is adapted to deliver a series of rotary impacts to the anvil;

(F) a first recessed annular groove formed in the hammer, accessible rearwardly of the hammer;

(G) an annular row of balls within the bottom of the first recessed annular groove;

(H) a second recessed annular groove formed in the radially-enlarged rearward portion of the spindle, accessible forwardly of the spindle; and

(I) a coiled spring disposed coaxially of the spindle, seated upon the annular row" of balls, and nested axially between the first and second recessed annular grooves formed on the hammer and the spindle, respectively, whereby the mechanism has minimum axial length for greater compactness.

2. In an impact wrench, the combination of:

(A) a motor having a shaft;

(B) a spindle coaxially aligned with the motor shaft and having a radially-enlarged rearward portion serving as a planet gear carrier;

(C) speed-reduction planetary gearing, interconnecting the motor shaft and spindle, and including a plurality of planet gears mounted on the carrier;

(D) a hammer coaxially mounted on the spindle forwardly of its planet gear carrier;

(E) an anvil forwardly of the hammer;

(F) cooperating clutch teeth formed on the anvil and hammer, respectively;

(G) cam means between the hammer and the spindle for imparting axial and rotary movement to the hammer relative to the spindle; whereby the hammer has axially advanced and retracted positions and is adapted to deliver a series of rotary impacts to the anvil; and whereby in its retracted position, the hammer telescopes over the planet gear carrier on the spindle;

(H) a first recessed annular groove formed in the hammer, accessible rearwardly of the hammer;

(I) a second recessed annular groove formed in the planet gear carrier, accessible forwardly of the spindle; and

(J) a coiled spring disposed lcoaxially of the spindle and nested axially between the first and second recessed annular grooves, respectively, whereby the mechanism has minimum axial length for greater compactness.

3. In a portable power-operated tool having a motor housing and a transmission housing extending forwardly therefrom, the combination of:

(A) a wall forming a partition between the motor housing and the transmission housing;

(B) bearing means within the wall;

(C) a motor in the motor housing, the motor having a shaft journaled in the bearing means and extending beyond the partition wall into the transmission housing;

(D) a pinion on the motor shaft;

(E) a spindle in the transmission housing, coaxially aligned with the motor shaft;

(F) said spindle having a rearwardly-extending tubular portion supported within the bearing means in the partition wall, radially of the motor shaft;

(G) a planet gear carrier mounted on the spindle, intermediately its length, for conjoint rotation therewith;

(H) pins mounted on the planet gear carrier;

(I) planet gears carried by the respective pins, engaging the pinion; and

(J) an internal ring gear on the partition wall, engaging the planet gears.

4. The combination of claim 3, wherein:

(A) said bearing means comprises a pair of coaxiallynested hollow-cylindrical bearings disposed radially of one another, one between the partition wall and the rearwardly-extending tubular portion of the spinly-cylindrical main housing comprising a motor housing 5 and an integrally-formed transmission housing extending forwardly therefrom, the combination of:

(A) a wall having an axially-extending annular flanged portion seated on a first annular ledge formed in the transmission housing forwardly of'the wall, the wall thereby serving as a partition between the transmission housing and the motor housing;

(B) a ring seated in an annular groove formed in the motor housing, rearwardly adjacent to the axiallyextending annular flanged portion of the partition wall;

(C) a retaining plate seated on a second annular ledge formed in the motor housing rearwardly of the partition wall;

(D) means securing the retaining plate to the wall, thereby drawing the wall up tight against the ring; and

(E) means preventing rotation of the retaining plate relative to the motor housing.

6. The combination of claim 5, wherein:

(A)' an internal ring gear is formed integrally within the axially-extending annular flanged portion of the partition wall.

7. The combination of claim 5, wherein:

(A) the partition wall has at least one bearing sleeve mounted therein; and wherein:

(B) a spindle is mounted in the transmission housing, the spindle having a rearwardlyextending port on journaled within the bearing sleeve in the partition wall;

(C) whereby the bearing sleeve abuts against the retaining plate, and whereby the retaining plate takes the rearward axial end thrust of the spindle.

8. An impact wrench, comprising:

(A) a generally-cylindrical main housing comprising a motor housing and a clutch housing integrally formed with the motor housing and extending forwardly therefrom;

(B) a wall serving as a partition between the motor housing and the clutch housing;

(C) bearing means in the partition wall;

(D) a motor in the motor housing, the motor having a shaft journaled in said bearing means and extending beyond the partition wall into the clutch housing;

(E) an anvil having a shank portion journaled in the forward end of the clutch housing;

(F) a spindle having a forward end piloted within the anvil shank and further having a rearwardly-extending tubular portion supported within the hearing means in the partition wall, radially of the motor shaft;

(G) a radially-enlarged planet gear carrier mounted on the spindle, intermediately its length, for conjoint rotation therewith;

(H) planet gears rotatably carried by the planet gear carrier and engaging the pinion on the motor shaft;

(I) an internal ring gear formed on the partition wall,

engaging the planet gears;

(I) a hammer coaxially mounted on the spindle;

(K) cooperating clutch teeth formed on the hammer and anvil, respectively;

(L) cam means between the hammer and the spindle for imparting axial and rotary movement to the hammer relative to the spindle; whereby the hammer has axially advanced and retracted positions and is adapted to deliver a series of rotary impacts to the anvil, and whereby in its retracted position, the hammer telescopes over the planet gear carrier on the spindle;

(M) a first recessed annular groove formed on the hammer, accessible rearwardly of the hammer;

(N) a second recessed annular groove formed on the planet gear carrier, accessible forwardly 'of the carrier; and

(O) a coiled spring disposed coaxially of the spindle and nested axially between the first and second recessed annular grooves in the hammer and planet gear carrier, respectively, thereby constantly urging the clutch teeth into engagement witheach other in opposition to the cam means;

(P) whereby the overall axial length of the impact wrench is minimized.

References Cited UNITED STATES PATENTS Hornschuch 173-93.6

CHARLES E. OCONNELL, Primary Examiner. NILE c. BYERS, JR, Examiner. 

8. AN IMPACT WRENCH, COMPRISING: (A) A GENERALLY-CYLINDRICAL MAIN HOUSING COMPRISING A MOTOR HOUSING AND A CLUTCH HOUSING INTEGRALLY FORMED WITH THE MOTOR HOUSING AND EXTENDING FORWARDLY THEREFROM; (B) A WALL SERVING AS A PARTITION BETWEEN THE MOTOR HOUSING AND THE CLUTCH HOUSING; (C) BEARING MEANS IN THE PARTITION WALL; (D) A MOTOR IN THE MOTOR HOUSING, THE MOTOR HAVING A SHAFT JOURNALED IN SAID BEARING MEANS AND EXTENDING BEYOND THE PARTITION WALL INTO THE CLUTCH HOUSING; (E) AN ANVIL HAVING A SHANK PORTION JOURNALED IN THE FORWARD END OF THE CLUTCH HOUSING; (F) A SPINDLE HAVING A FORWARD END PILOTED WITHIN THE ANVIL SHANK AND FURTHER HAVING A REARWARDLY-EXTENDING TUBULAR PORTION SUPPORTED WITHIN THE BEARING MEANS IN THE PARTITION WALL, RADIALLY OF THE MOTOR SHAFT; (G) A RADIALLY-ENLARGED PLANET GEAR CARRIER MOUNTED ON THE SPINDLE, INTERMEDIATELY ITS LENGTH, FOR CONJOINT ROTATION THEREWITH; (H) PLANET GEARS ROTATABLY CARRIED BY THE PLANET GEAR CARRIER AND ENGAGING THE PINION ON THE MOTOR SHAFT; (I) AN INTERNAL RING GEAR FORMED ON THE PARTITION WALL, ENGAGING THE PLANET GEARS; (J) A HAMMER COAXIALLY MOUNTED ON THE SPINDLE; (K) COOPERATING CLUTCH TEETH FORMED ON THE HAMMER AND ANVIL, RESPECTIVELY; (L) CAM MEANS BETWEEN THE HAMMER AND THE SPINDLE FOR IMPARTING AXIAL AND ROTARY MOVEMENT TO THE HAMMER RELATIVE TO THE SPINDLE; WHEREBY THE HAMMER HAS AXIALLY ADVANCED AND RETRACTED POSITIONS AND IS ADAPTED TO DELIVER A SERIES OF ROTARY IMPACTS TO THE ANVIL, AND WHEREBY IN ITS RETRACTED POSITION, THE HAMMER TELESCOPES OVER THE PLANET GEAR CARRIER ON THE SPINDLE; (M) A FIRST RECESSED ANNULAR GROOVE FORMED ON THE HAMMER, ACCESSIBLE REARWARDLY OF THE HAMMER; (N) A SECOND RECESSED ANNULAR GROOVE FORMED ON THE PLANET GEAR CARRIER, ACCESSIBLE FORWARDLY OF THE CARRIER; AND (O) A COILED SPRING DISPOSED COAXIALLY OF THE SPINDLE AND NESTED AXIALLY BETWEEN THE FIRST AND SECOND RECESSED ANNULAR GROOVES IN THE HAMMER AND PLANET GEAR CARRIER, RESPECTIVELY, THEREBY CONSTANTLY URGING THE CLUTCH TEETH INTO ENGAGEMENT WITH EACH OTHER IN OPPOSITION TO THE CAM MEANS; (P) WHEREBY THE OVERALL AXIAL LENGTH OF THE IMPACT WRENCH IS MINIMIZED. 